The morphology and patency of arterial and venous microvascular anastomoses throughout the first post-operative year. A histological study.

End-to-end microvascular suture anastomoses, 40 arterial and 41 venous, from the rabbits carotid artery and posterior facial vein were harvested at 5 different time intervals (1, 2, 3, 6 and 12 months) post surgery and evaluated with light microscopy. A 100% long-term patency was noted both in arteries and veins. Quantitative measurements of the width of the vessel wall components indicated that a statistically significant temporary hypertrophic response occurred in the arterial intima, culminating in the third month when the width of the vessel wall at the anastomotic level almost doubled the normal. After that the width of the vessel wall again declined but it remained thicker than the adjacent vessel wall at one year post surgery. Among the venous anastomoses, however, the wall thickness at the anastomotic level remained thinner than the adjacent vessel wall throughout the evaluation period. The original vessel wall characteristics are not restored at the anastomotic site with intimal hyperplasia compensating for medial necrosis. Despite these events a technically satisfactory microvascular anastomosis should remain patent for years.

Free flaps and irradiated recipient vessels: an experimental study in rabbits.

In an experimental study in rabbits the effect of previous irradiation to the recipient vessels on the survival rate of free flaps was evaluated. Pre-operative radiotherapy was given in a single anterior neck field using a Cobalt60 unit, 1.25 MeV, SSD 80 cm in a fractionated dose corresponding to 5000 rad/5 weeks. An experimental model using paired data was established using two epigastric free flaps in each animal: one anastomosed to the irradiated vessels (carotid and jugular vein) and implanted outside the irradiated field and the other flap anastomosed to the normal femoral vessels and also implanted outside the irradiated field. In a sequential analysis it was found that free flaps anastomosed to irradiated recipient vessels within 12 weeks from the start of radiotherapy failed significantly more often than free flaps anastomosed to normal recipient vessels (p less than 0.10). This supports the view that preference should be given to the use of non-irradiated recipient vessels for microvascular transfer of free flaps.

Healing of microvascular anastomoses. A comparative study using normal and irradiated recipient vessels for experimental free flaps in rabbits.

A comparative study was undertaken to evaluate the possible effect of previous radiotherapy on the healing of subsequently performed microvascular anastomoses between irradiated recipient vessels and normal flap vessels in rabbits. Radiotherapy was given preoperatively to a single anterior neck field using a Cobalt 60 unit, 1.25 MeV, SSD 80 cm in a fractionated dose corresponding to 5,000 rad/5 weeks. An experimental model using paired data was established using two epigastric free island flaps in each animal: one anastomosed to the irradiated vessels (carotid artery and jugular vein) and the other anastomosed to the normal opposite femoral vessels. Results did not show any marked difference in the healing pattern during the first 3-week period postoperatively except for a higher rate of thrombosis, when irradiated recipient vessels were used in end-to-end anastomoses, while no difference in healing pattern or rate of thrombosis were found using telescoped arterial anastomoses.